Tamara I. Balakhnina

Effects of silicon on plant resistance to environmental stresses: review

Abstract The role of exogenous silicon in enhancing plant resistance to various abiotic stressors: salinity, drought, metal toxicities and ultraviolet radiation are presented. The data on possible involvement of silicon in reducing the reactive oxygen species generation, intensity of lipid peroxidation, and in some cases, increasing the activity of enzymes of the reactive oxygen species detoxificators: superoxide dismutase, ascorbate peroxidase, glutathione reductase, guaiacol peroxidase and catalase are analyzed.

The effect of soil aeration on superoxide dismutase activity, malondialdehyde level, pigment content and stomatal diffusive resistance in maize seedlings

Abstract Deficient soil aeration that causes hypoxia of maize roots frequently decreases plant biomass production. Characterizing relationships among maize physiological responses to varying levels of root hypoxia is critical to predicting maize plant biomass production. Maize seedlings 12 days old were subjected to increasing root hypoxia over a 12 day period by increasing soil water content in 0.06–0.07 m 3 m −3 intervals up to soil saturation. Soil hypoxia conditions were characterized by measuring air-filled porosity (Eg), oxygen diffusion rate (ODR), and redox potential (Eh). The objective of the study was to verify the hypothesis that some physiological parameters can be used to relate levels of soil hypoxia to biomass production. It was found that soil hypoxia caused a decrease of shoot and root biomass, and diminuished the content of leaf protein, chlorophyll, carotenoid, and malondialdehyde (MDA). An increase, due to hypoxia, was observed in the case of stomatal diffusive resistance (Rd) during the entire stress period and of leaf superoxide dismutase (SOD) activity after 8 and 12 days. The SOD activity in the roots increased after 2 and 8 days of hypoxia and decreased after 12 days. The results confirm the hypothesis that the shoot physiological parameters of maize plants can be used to relate varying levels of soil hypoxia to biomass production. The most promising seems to be Rd and SOD activity. The best indicator of the soil aeration status appeared to be ODR.

Effects of silicon on growth processes and adaptive potential of barley plants under optimal soil watering and flooding

Barley (Hordeum vulgare L.) was grown in pots with brown loess soil and highly soluble amorphous silicon dioxide as the source of monosilicic acid to examine its influence on plant growth and adaptive potential under optimal soil watering and flooding. The adaptive potential of plants was estimated by the concentration of the thiobarbituric acid reactive substances (TBARs) as well as superoxide dismutase (SOD), guaiacol peroxidase (GPX) and ascorbate peroxidase (AsP) activities. Application of amorphous silica to the soil increased the Si content in barley shoots and roots and stimulated their growth and biomass production under optimal soil watering. Soil flooding suppressed the growth both of the (−Si)- and (+Si)-plants. The intensity of oxidative destruction estimated by the concentration of TBARs was lower in the roots and leaves of the (+Si)-plants. Soil flooding induced SOD activity in the roots and in the leaves of the (−Si;+flooding) and (+Si;+flooding)-plants, but no significant differences were observed due to the Si treatment. GPX activity in the roots of (+Si)-plants was higher than in the (−Si)-ones under optimal soil watering, but under soil flooding no differences between (+Si)- and (−Si)-treatments were observed. AsP activity was not influenced by Si treatment neither under optimal soil watering nor under flooding. Thus, application of Si stimulates growth processes of barley shoots and roots under optimal soil watering and decreases intensity of oxidative destruction under soil flooding without significant changes in the activities of antioxidant enzymes.

Heat-induced impairments and recovery of photosynthetic machinery in wheat seedlings. Role of light and prooxidant-antioxidant balance

The extent of damage caused to the photosynthetic machinery of 10-d-old wheat seedlings by short-term exposure to mild heat, their capacity to recover from it and the possible roles of H2O2, SOD, catalase and ascorbate peroxidase on the recovery process were investigated. Seedlings were subjected to heat treatments at 40/42/44 °C for 20 min in the dark and allowed to grow for 72 h in light of different irradiances (40–800 μE m−2 s−1) at 20 °C for recovery from heat induced damage. Complete or partial recovery of photosynthetic activities was observed in the seedlings treated at 40 °C and 42 °C, but not at 44 °C. Our data suggest that the balance between (pro)oxidant and antioxidant levels poised by heat stress subsequent light is the crucial factor for the extent of recovery from heat induced damage.

Stress responses of spring rape plants to soil flooding

Abstract Stress responses of spring rape to soil hypoxia were investigated during 8-days flooding. Soil air-filled porosity decreased from 25-30% to 0%, oxygen diffusion rate - from 2.6-3.5 to 0.34 μmol O2 m-2 s-1, and redox potential - from 460 to 150mVwithin few hours. Alcohol dehydrogenase activity in roots increased up to 7-fold after one day of flooding and then decreased to 170% of control. Superoxide dismutase activity in roots increased by 27% during first 3 days and then dropped to 60% of control; in the leaves superoxide dismutase activity increased in average by 44%. Ascorbate peroxidase activity in leaves increased by 37% during first 3 days and then decreased to control value. Glutathione reductase activity increased by 45% in roots of flooded plants but did not change in leaves. Proline concentration in leaves increased up to 4-fold on the 3d day of flooding and then decreased to control value. Thus soil flooding induces increase of alcohol dehydrogenase activity and subsequent increase of superoxide dismutase and glutathione reductase activities in roots while the leaves display a few days increase of free proline concentration and ascorbate peroxidase activity, and a long-term increase of superoxide dismutase activity.

Effect of temperature on oxidative stress induced by lead in the leaves of Plantago major L.

Abstract Fluctuation of the summer day-time temperatures in the mid-latitudes in a range from 16 to 30°C should not have irreversible negative effects on plants, but may influence metabolic processes including the oxidative stress. To test the effect of moderately high temperature on oxidative stress induced by lead in the leaves of Plantago major L.; the plants were incubated in a water solution of 0, 150, 450, and 900 μM Pb (NO3)2 at 20 and 28°C. Plant reactions were evaluated by the content of thiobarbituric acid reactive substances and ascorbate peroxidase and glutathione reductase activities in leaves after 2, 24, 48, and 72 h. The Pb concentration in the leaves rose with the increase in the Pb content and was higher at 20°C. The increase in stomatal resistance caused by Pb was higher at 28°C. The contents of TBARS increased after 2 h of plant exposure to Pb and the increase was the highest at 900 μM Pb, 28°C. The AsP activity increased up to 50% after 24 h of Pb-treatment at 28°C; the highest increase in glutathione reductase activity was observed after 72 h at 20°C. Thus, the moderately high temperature 28°C compared with optimal 20°C caused a decrease in Pb accumulation in Plantago leaves but amplified the negative effects of lead, especially in the beginning of stress development.

Plant Responses to Soil Flooding

The influence of various extent of soil moisture and its aeration status in the root zone of the plants on the physiological status and defensive system against oxidative destruction of the tolerant-to-soil-flooding maize Zea mays L. and sensitive pea Pisum sativum L. was investigated. The efficiency of the defensive system was evaluated by the activity of SOD as an enzyme neutralizing superoxide anion radicals, by MDA content indicating the rate of free radical lipid oxidation, and by the root and shoot biomass production and pigment concentration in the leaves. Plant resistance to the effects of soil flooding depends not only on the ability to survive at the action of soil hypoxia but also on the subsequent reoxygenation. The effects of prolonged soil hypoxia and subsequent re-aeration on the development of the stress-realizing system bean Vicia faba major L. cv. Bartom plants were investigated. In connection with the specificity of the effect of hypoxia on the plants, the specific and nonspecific plant responses to the effect of this stress factor were investigated. In this case special attention was paid to the changes connected with transformations of respiration pathways, with functioning of the root alcohol dehydrogenase in the spring rape Brassica napus L. Formation of the reactive oxygen species which appears to be a unspecific plant response to different stress factors, including hypoxia, was estimated by the intensity of oxidative destruction processes and activity of antioxidant enzymes in plant tissues.

Mechanism of enhancing photosystem 2 thermoresistance in wheat plants by chlorocholine chloride.

It is shown that pretreatment of wheat seeds with chlorocholine chloride reduces inhibition of photosystem 2 activity in the first leaves of 10-day-old wheat variety Moskovskaya 35 seedlings caused by heating at 39–41°C for 5–20 min and improves its poststress recovery, probably due to activation of antioxidant enzymes and increase in the level of low molecular weight antioxidants.

Aftereffect of heat shock on activity of the photosynthetic apparatus and lipid peroxidation in wheat leaves

AbstractsThe dynamics of development of oxidative stress and poststress recovery of the photosynthetic apparatus in leaves of 10-day-old wheat seedlings subjected to heat shock (40, 42, and 44°C) for 20 min and exposed to light for 72 h are studied. The effect of pretreatment temperature and light intensity on recovery of the photosynthetic apparatus and its resistance to photostress and repeated heat shock is examined.